This project is concerned with the dynamic behavior of the brain and spinal cord under impact loading. The quantitative biomechanical data obtained are correlated with the neurological, evoked potential and neurochemical assessments post-trauma. The main foci of our group will be on: 1) The accurate and continuous measurements of the head impact force, the induced dynamic skull acceleration and intracranial pressure, in the adolescent rhesus macaque, during laboratory-induced frontal impact to its unrestrained head and neck. 2) The continuous monitoring of some standard physiological parameters such as EKG, systemic arterial and central venous pressures, entidal pCO2 and somatosensory evoked potential pre- and post-impact. 3) The dynamic, in vitro material properties and failure characteristics of the spine with special emphasis on the cervical region. 4) The construction of a structural finite-element computer model of the head and neck of the rhesus during direct head impact, based on the in vivo constituent and gross mechanical response data. The experimentally measured pressure and acceleration will serve to validate this class of computer models for simulation purposes. 5) The neurochemical studies seek to determine whether neuronal destruction occurs over prolonged (1 week) or a short (24 hour) period following impact. By measuring the levels of neurohormones (norepinephrine, dopamine, 5-hydroxytryptamine and synthesizing marker enzymes decarboxylase and dopamine-beta-hydroxylase) data will be obtained to determine whether regeneration or sprouting of neuronal terminal projections occurs at various times (up to 3 months) after injury. These studies will provide informaton for direct application in the prevention, diagnosis and treatment of head injury because of the obvious logistic, methodologic and statistical advantages of our multi-variable and multi-disciplinary approach to this major biomedical problem.